Television receiver



sept. 17, 1946. R DESERNO Y 2,407,654

TELEVI S ION RECEIVER Filed March '29, 1940 fmfenar:

Feier esezwo 4 Patented Sept. 17, 1946 2,407,654 TELEVISION RECEIVER Peter Deserno, Berlin, Germany; vested in the Alien Property Custodian Application March 29, 1940, Serial No. 32.6,565 In Germany March 17, 1939 3 Claims. 1

In television receivers the automatic amplitude regulation meets with diiculties. The simple expedient of forming a mean value of the high frequency energy in order to produce the regulating voltage is not possible because the mean value changes in accordance with `the luminosity values of the picture. In the case of bright pictures the mean value would be greater than Iwith dark ones.

Transmitting arrangements are known which are based on the so-called gap synchronization, that is, a synchronizing method in which the picture signals increase toward positive values from an amplitude that corresponds to the black value of the incoming signal voltage, while the synchronizing signals are extended from the black value in the reverse direction toward the zero value. With these transmitting arrangements a regulating voltage may be obtained by taking from the frequency mixture the amplitude which is equivalent to the black value. This amplitude merely depends upon the magnitude of the received high frequency energy, being independent of the luminosity values of the picture.

According to the invention, in order to produce the regulating voltage equivalent to the black value the synchronizing signals are ltered out from the rectified frequency mixture, which contains the picture and synchronizing signals, by means of a choke device while the remainder of this mixture is conveyed to a condenser in such manner that its potential shall rise to become equal to the black value. To such end the voltage supplied to the condenser passes through a rectifier which prevents back discharge of the condenser over the feeding source, such as a coupling" resistance. The condenser is thus always charged to the maximum value of the feeding voltage. The voltage supplied to the condenser is applied to it with such ,a polarity that its potential increases whenever the arriving voltage varies toward the black value.

Thel choke device by which the synchronizing signals are filtered out from the rectified frequency mixture is dimensioned to cut off all such frequencies as are above line frequency. The Voltage at the condenser will hence not be able to increase beyond the black value, the synchronizing impulses having been segregated.

In order to enable the potential at the condenser to decrease in accordance with the black value whenever the receiving amplitude increases, a resistance is connected in parallel with this condenser. Such resistance and condenser are calculated to afford a time constant that accords with the duration of several picture periods, such as a second.

In the accompanying drawing, Fig. 1 is a circuit diagram showing one embodiment of the invention, while Figs. 2 and 3 illustrate curves referred to in explaining the function of this embodiment.

An electron tube H, Fig. l, is the last stage of the intermediate frequency amplifier of a television receiver. To this tube a nal tube G1 is connected through a transformer T. Tube G1 is arranged to act as a rectifier in known manner. The potential arising at a resistance W and a condenser K acts to control the anode current of tube Gi by means of a control grid thereof, as will be seen in Fig. 1. In the cathode lead of the tube Gi a coupling resistance A is included which is grounded in unipolar fashion. At resistance'A a voltage arises that corresponds to the rectified frequency mixture containing picture and synchronizing signals. The curve UA of this voltage is illustrated in Fig. 2.

A choke coil D acts to cut off all those frequencies which are above line frequency. At points P, Q a voltage UPQ, Fig. 3, is effective which has the synchronizing impulses segregated. 'Ihe maximum value of this voltage hence equals the black Value of the incoming voltage, as will be understood from Fig. 3. Condenser C thus charges to acquire a potential Uc that corresponds to the black value.

Rectier G2 prevents the condenser from discharging through resistance A. Condenser C discharges over resistance R. whenever the dark value changes. The dimensions are such that condenser and resistance shall afford a time constant of about a second.

The regulating voltage is derived from condenser C, as indicated by the arrowed line QC, in order to be conveyed to a control tube or several such tubes.

What is claimed is:

1. A device for regulating the amplitudes in television receivers by a voltage equivalent to the black value of the incoming signal voltage, which comprises means for rectifying a frequency mixture containing picture and synchronizing signals, said means including an output resistor having a positive and a negative terminal,` a rectilier having an anode connected to said positive terminal and a cathode, a storage circuit combination comprising a resistance and a condenser connected in parallel, connections from one end of said combination to said cathode and from the other end of said combination to said negative terminal, and a choke device for removing the synchronizing signals from said frequency mixture, whereby the condenser is charged to a potential corresponding to said black value..

2. A device according to claim 1, wherein said choke device is adapted to cut olf all frequencies above line frequency.

3. A device according to claim 1, wherein said resistance and condenser combination is adapted to aord a time constant defined by the duration of a number of picture periods.

PETER DESERNO. 

